1. Field of the Invention
The present invention relates to a photographing apparatus and method for obtaining an image by photographing, such as a digital camera, and the like. The invention also relates to a computer program product for causing a computer to perform the photographing method.
2. Description of the Related Art
In photography with digital cameras, it is customary to detect a target object, such as a face or the like, from an image obtained by photographing and to change the conditions for image processing performed on the image or photographing conditions when photographing according to the detection result of the target object. When the target object is a face, in particular, it is also customary to count the number of detected faces and to record the image after trimming the detected faces.
For detecting a target object from an image and performing various types of image processing on the image as described above, it is necessary to accurately detect the target object from the image. Consequently, different methods for accurately detecting a target object have been proposed. For example, a method is proposed as described, for example, in Japanese Unexamined Patent Publication No. 2002-183734, in which when authenticating the identity of an authentication target person by photographing a face image of the authentication target person, extracting a characteristic amount of the face of the target authentication person from the face image, calculating a similarity level between the extracted characteristic amount and a reference characteristic amount, and making a comparison between the calculated similarity level and a threshold value, the threshold value is changed according to whether or not the authentication is performed within a high use time of the authentication target person, thereby improving the successful authentication ratio during the high use time of the authentication target person.
Another method is also proposed as described, for example, in U.S. Patent Application Publication No. 20050069208, in which face candidates are detected from an image, and a face candidate that does not satisfy predetermined conditions, such as the case where the color dispersion value of the face candidate is small, or the occupation ratio of a flesh color region is large, is determined to be a non-face and precluded from detected face candidates.
The methods described in the aforementioned patent publications may improve face authentication accuracy or face detection accuracy, but the demand for further improving the accuracy still exists.
The present invention has been developed in view of the circumstances described above, and it is an object of the present invention to further improve the accuracy for detecting a face from an image.